Add Docker deployment pipeline and site updates

- Dockerfile (multi-stage Next.js standalone build)
- docker-compose.yml for Portainer stack
- Gitea Actions workflow for CI/CD
- Runner container config (Dockerfile.runner + compose)
- next.config.ts: enable standalone output
- Site content and image updates

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.runner.yml

@@ -0,0 +1,18 @@
+services:
+  runner:
+    build:
+      context: .
+      dockerfile: Dockerfile.runner
+    restart: unless-stopped
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+      - /opt/micromelon:/opt/micromelon
+      - runner-data:/data
+    environment:
+      GITEA_INSTANCE_URL: ${GITEA_URL}
+      GITEA_RUNNER_REGISTRATION_TOKEN: ${RUNNER_TOKEN}
+      GITEA_RUNNER_NAME: micromelon-runner
+      GITEA_RUNNER_LABELS: "self-hosted:host"
+
+volumes:
+  runner-data: